The present invention relates to a hand crusher to be used for dismembering concrete structures and the like.
In general, hydraulic crusher is used for crushing and dismembering concrete structures because high pressure is needed for the purpose, whereas a hand crusher is used when working space is small.
FIG. 8 shows the structure of a conventional type hand crusher, in which a pair of crushing arms 65 and 66 are pivotally supported at opposite positions by support pins 63 and 64 at both ends of a center link 62. The opposing crushing arms 65 and 66 are provided with toothed portions 65a and 66a on the lower parts and the end portions 65b and 66b on the upper ends. Further, the end portion 65b is connected to the connecting unit 69a of hydraulic cylinder 69 through a pin 67, and the end portion 66b is connected to the connecting unit 70a of a piston rod 70 of hydraulic cylinder 69 through a pin 68. On the left end and the right end of the connecting units 69a and 70a, grips 60 and 61 for hand gripping are furnished.
Therefore, when hydraulic pressure is applied during crushing operation, the piston rod 70 is extended from the hydraulic cylinder 69, widening the distance between the end portions 65b and 66b and closing the gap between the opposing toothed portions 65a and 66a. Thus, crushing operation is carried out.
In the conventional type equipment as described above, the operator grasps the grips 60 and 61 during crushing operation and lifts up heavy equipment, and the distance between the left and the right grips 60 and 61 is widened. Accordingly, it is necessary to move the positions of arms rapidly. Further, much force is required to maintain the equipment by unstable grips 60 and 61, which move to left and right, and wide working space is needed for the crushing operation.
Also, as shown in FIG. 9, when the object to be crushed 36 is caught between the toothed portions 65a and 66a of a pair of arms 65 and 66 from oblique direction (the direction A--A), rotation moment toward counterclockwise direction (the direction C) is generated as the engaging force of the toothed portions 65a and 66a is increase application of pressure, and pressure is applied on the object 36 from the direction perpendicular to it (the direction B--B). The toothed portions 65a and 66a finally crush the object 36 with big crushing force from the perpendicular direction (the direction . B--B), where rotation moment is turned to zero.
Therefore, when the object to be crushed 36 is not fixed on floor surface, the object is rotated clockwise (reverse to the direction C) and is crushed when the left and the right grips 60 and 61 are held firmly, while the object 36 is swung around and danger may occur as it hits the operator or other objects nearby.
When the object to be crushed 36 is fixed on floor surface, the toothed portions 65a and 66a are rotated by reaction force, and the left and the right grips 60 and 61 connected integrally with the toothed portions are swung around, and there is a possibility that the operator may be hit. In this way, in case of a conventional type hand crusher, when the object to be crushed 36 is caught from oblique direction, rotation moment is generated by reaction force, and the grips 60 and 61 or the object 36 are swung around. Thus, it is necessary for the operator to take special care not to catch the object from oblique direction, and this means heavy mental burden on the operator.
Therefore, in an unstable conventional type crusher with the left and the right grips moving to left and right during crushing operation, it is impossible to operate it by a single operator. There must be one operator each to hold the left and the right grips 60 and 61 respectively, and two operators are to be assigned on one crusher to carry out the crushing operation.